-- violence especially painful at Fort Hood where they are still dealing with all the fallout from that 2009 she -- -- commit more on this from ABC's Martha Raddatz. And -- the big question every when they're asking how could this happen again. Georgia these are very different cases first of all you had Nadal Hasan who said he thought the US military was waging a war against Islam. And this where you had a soldier suffering from depression anxiety and being looked at for post dramatic stress. This much more resembles a case in May of 2009 in Baghdad where a soldier getting mental health treatment. Opened fire in a mental health facility there in Baghdad. And he killed five so it's very similar to that one and Martha we know these problems posttraumatic stress so prevalent for veterans of Iraq and Afghanistan up to one in five. Veterans of those -- may have PT SD. Did exactly and this also may be a real wake up call for the military issue said one in fine service members suffer from post traumatic stress syndrome or any sort out other mental health issues. But it is very important to stress George that violence against others is not rampant among those who suffer PT SD. They -- trying to.

This transcript has been automatically generated and may not be 100% accurate.

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